Is it permissible to donate the value of wasted hours over 15 years from the monthly retirement salary after calculating it as a percentage of the salary?

If you owe money to a workplace, it must be returned to them, even if indirectly, to clear your conscience. Donating it as charity is not sufficient unless its return is impossible. You must hasten to do so without delay, because it is unknown whether your life will be prolonged or not, whether you will maintain the intention to donate it as charity or not, and whether the heirs will fulfill this after your death or not.